Shiny, reflecting external surfaces of the superstructures and of the hull above the waterline are particularly desired in yacht building. To achieve this, the undercoats onto which the corresponding shiny coating systems are applied, must be uniform and smooth. Larger ships, from a length of approximately 50 meters, are usually made of steel sheets so that they exhibit typical processing traces such as welding seams. The entire hull, inclusive of the superstructures, is normally processed manually before any varnishing to obtain a uniform, faultless surface. Irregularities are thereby filled by applying a putty or a filler. The surface is sanded smooth once the filler has hardened. These working steps are repeated until the necessary surface quality has been reached. The strength of the filler layer depends on the roughness of the surface. Filler layers up to several centimeter thickness can be applied to obtain the necessary uniformity and smoothness.
Particular requirements should be met with such layer thicknesses. The hardened filler must be sufficiently elastic to avoid the formation of cracks in the filler layer, for example, in case of deformations of the hull or of temperature fluctuations. The density of the filler also plays a major part. The hardened fillers should have a comparatively minimal density to increase the total weight of the ship as little as possible with the quantities of filler masses used.
Two-component putties based on epoxy resins have to date been used. Hollow spheres of glass can be added thereto as light filling materials to reach a density of between 0.5 and 1 g/cm3. These putties cannot be processed with the usual machines for processing two-component systems. The common processing machines pump both components from their respective storage containers into a mixing chamber, mix them, and evacuate the mixture out of the machine. Common modes of discharge are known to a person of skill in the art such as, for example, casting, laying up of caterpillars, and hydraulic or compressed air supported sputtering. The pressures and shear forces exerted onto the putties cause the destruction of the hollow spheres of glass. This destruction increases the density of the putty so that the hardened filler becomes significantly denser. Mechanical properties, for example, the elasticity of the hardened filler, also worsen. Ships have therefore been worked on manually using time-consuming and costly methods.
EP 1103310, also published as DE 60034646, describes a mechanical coating method in which putties according to U.S. Pat. No. 5,571,312 are used. The two-component putties on the basis of epoxy resins contain ceramic hollow spheres, among others, as a filling material. They are mechanically sufficiently stable so that they can be mechanically processed without destruction, but they have a significantly greater density than hollow spheres of glass.